Notes on delimitation

Recent molecular phylogenetic work on Icacinaceae (Kårehed, 2001) has demonstrated that the family should be split into four families: Icacinaceae s. str. (Garryales), Pennantiaceae (a member of order Apiales), Cardiopteridaceae, and Stemonuraceae (both members of order Aquifoliales).

The family Cardiopteridaceae includes three genera from the Old World, and Citronella D. Don, and possibly Dendrobangia Rusby from the New World. The family Stemonuraceae includes eleven genera from the Old World (e.g. Gomphandra Wall. ex Lindl., Stemonurus Blume, and Codiocarpus R. A. Howard) and Discophora Miers from the New World.

Finally, Icacinaceae s. str. includes nine Neotropical genera. Metteniusa H. Karst. have historically generated considerable systematic dispute but a recent phylogenetic analysis based on a combined dataset of three genes demonstrated that the genus must be considered a different monogeneric family: Metteniusaceae. This family is included in the lamiids clade but as an isolated taxon in the base of a clade including Boraginaceae, Vahliaceae, Gentianales, Lamiales, and Solanales (González et al., 2007). Garryales and the family Icacinaceae form another clade in the lamiids.

Unilocular ovary (multilocular in Emmotum Desv. in Ham.) with two pendulous ovules.

Other important characters

Icacinaceae are mostly trees or vines, sometimes shrubs with scandent branches.The most conspicuous character of the family is the ovary: 1-locular, rarely 2-3-locular with two ovules, apical, pendulous, anatropous and unitegmic.

Small domatia are found in the abaxial surface of Citronella and Mappia.

Indumentation is very common and variable in the family. Heintzelmann & Howard (1948) found at least 10 types of hairs in that family.

The inflorescence is generally axillary, sometimes terminal or opposite to the leaves (Citronella); it is variable, ranging from one or two flowers for extreme reduction as in Ottoschultzia, to a raceme, thyrse or cyme, sometimes very modified as a pseudo-spike in female plants of Calatola or as a spiciform raceme in Pleurisanthes.

Flowers are very small and the pedicel is generally articulated at the base of the flower (not in Pleurisanthes). They are generally bisexual, and less commonly completely unisexual bearing only stamens or pistil, as in Calatola.

A typical bisexualflower generally has 5 parts, rarely four (as in Calatola).

Key differences from similar families

The genus Metteniusa with seven species distributed through Costa Rica, Panama, Colombia, Venezuela, Ecuador and Peru has cymose inflorescences with large flowers and long sagittate, moniliform stamens.

Number of genera

Calatola Standl.

Casimirella Hassl.

Citronella D. Don

Dendrobangia Rusby

Discophora Miers.

Emmotum Desv. in Ham.

Leretia Vell.

Mappia Jacq.

Oecopetalum Greenm. & C.H. Thomps.

Ottoschulzia Urb.

Pleurisanthes Baill.

Poraqueiba Aubl.

Useful tips for generic identification

Citronella and Dendrobangia (which may be considered as members of the family Cardiopteridaceae) can be differentiated in the first case by:

Fruits flattened, slightly arcuate, bearing a large oblongfleshyappendage of a lighter color on the concave side, the pericarp dark, fleshy, the putamen with ribs and mainly convex sides.

Notable genera and distinguishing features

Emmotum is the biggest genus with 13 species found in the Guayana Shield and the Amazon basin. It is a unique genus with multilocular ovary.

Citronella with 8-10 species, still has many problems for recognition at specific level.

Status

Icacinaceae genera are mostly endemic to major phytogeographical realms. One exception is Citronella, which is shared by America, Asia and Oceania. Twelve genera and approximately 50 species occur naturally in the New World. Most New World Icacinaceae genera are found within the tropics, a few species occur in subtropical regions, and one species outside of these (Citronella mucronata at 45° S). Most New World genera are widespread in the region, but Oecopetalum is confined to Southern Mexico and Central America, and Mappia and Ottoschultzia to Southern Mexico, Mesoamerica and the Caribbean region.

In America only two species are economically important. Poraqueiba sericea has a fleshyfruit rich in oil that is eaten fresh, also seeds that can provide flour. The fruit is widely traded throughout the Amazon basin. Also Casimirella ampla produces a tuber weighing 5-20 kilos, rich in starch that is edible after washing out the bitter-tasting compounds.

General notes

Most Neotropical genera of the family Icacinaceaes. str. were not included in the molecular analysis of Kårehed (2001) and their position within the lamiid clade needs to be confirmed.